If you've found blood in the toilet or on the paper after going to the toilet, you're understandably worried — and you're right to take it seriously. For most people, the cause turns out to be something benign like haemorrhoids or a small tear called an anal fissure. But rectal bleeding should never just be brushed off, because bowel cancer and other important conditions can produce exactly the same symptom, often without any other warning signs at all.
The good news is that when bowel cancer is found early, it is very treatable — and the way you find it early is by getting assessed rather than waiting. Seeking a review now, rather than watching to see if the bleeding settles, is the right call.
Bright red blood on the paper or on the outside of the stool most commonly comes from somewhere close to the anal opening — the lower bowel, anal canal, or rectum. Haemorrhoids, an anal fissure (a small tear), or rectal polyps are the usual culprits.
Dark red or maroon blood mixed into the stool suggests the bleeding is coming from higher up in the colon or even the small bowel, which is more likely to mean something significant needs investigation.
Black, tarry stool (called melaena) means the blood has been digested — it's coming from much higher up, like the stomach or upper digestive tract. This needs urgent assessment.
The colour of blood alone can't reliably tell you whether it's serious or not. Any rectal bleeding is worth having assessed by a specialist — regardless of what colour it is or how much there was.
Haemorrhoids
The most common cause. Haemorrhoids typically produce bright red blood on the paper or in the toilet bowl, separate from the stool. There may also be some perianal discomfort, a lump that appears after a bowel motion (prolapse), or a mucous discharge. One important thing to remember: haemorrhoids and bowel cancer can exist at the same time. Having a known history of haemorrhoids doesn't mean something more serious has been ruled out.
Anal fissure
A small tear in the lining of the anal canal. It usually produces a small smear of bright red blood, but the giveaway is pain — often sharp or burning — during and after going to the toilet. Common after constipation or childbirth.
Bowel polyps
Adenomatous polyps — growths on the bowel wall that can eventually turn cancerous — sometimes bleed before they become a problem. They rarely cause obvious symptoms, which is why a colonoscopy is the only reliable way to find and remove them.
Bowel cancer
Colorectal cancer is the second most common cancer in Australia, affecting about 1 in 17 people over a lifetime. Rectal bleeding is one of its most common early symptoms — and in many cases, it's the only symptom. Cancer on the right side of the bowel may not produce visible blood at all; sometimes it is only picked up by a stool test (FOBT) that detects microscopic traces.
Diverticular bleeding
Diverticula are small pouches that form in the wall of the colon. They can occasionally bleed — usually a sudden, painless episode of a substantial amount of bright red or dark red blood. Most diverticular bleeds stop on their own, but they always need investigation to confirm the source.
Inflammatory bowel disease
Crohn's disease and ulcerative colitis can cause ongoing or recurring rectal bleeding, usually alongside diarrhoea, urgency, and cramping. If that combination sounds familiar, it's worth mentioning to your GP.
For any rectal bleeding, aim to see your GP within a few days rather than waiting to see if it goes away. Go to a doctor urgently or to an emergency department if:
- The bleeding is heavy — soaking through pads or passing clots
- You feel lightheaded, faint, or short of breath
- You also have severe abdominal pain
- You're on blood thinners or have a known bleeding condition
After reviewing your history and examining you, investigation usually involves a colonoscopy — the most thorough way to look at the entire large bowel and find the source of bleeding. The helpful thing about colonoscopy is that if a polyp or bleeding haemorrhoid is found, it can often be treated at the same time during the same procedure.
In some situations, other investigations may be more appropriate — such as a flexible sigmoidoscopy, CT colonography, or CT angiography. Your specialist will guide you on what's right for your circumstances.
Most rectal bleeding does have a benign cause — but you cannot know that until it has been properly assessed. A colonoscopy takes about 20–45 minutes and gives you a definitive answer. Finding something harmless is reassuring. Finding a polyp or early cancer means it can be treated at a stage when treatment is most effective. Waiting to see if things settle is the one option that does not serve you well.
If you've noticed blood after a bowel motion, ask your GP for a referral to a colorectal surgeon. A referral to Mr Nguyen at North Eastern Surgical can be made by your GP — call (03) 9816 3951.
Yes. Even a single, small episode of rectal bleeding is worth having checked. It is tempting to wait and see — most people do — but a one-off bleed can still be the first warning sign of a polyp or early cancer. A short consultation and, if needed, a colonoscopy will give you a definitive answer rather than weeks of worrying.
It could be, but you cannot assume it is. Haemorrhoids and bowel cancer can occur together, and one of the most common ways people delay a cancer diagnosis is by putting bleeding down to "just the piles." If you have a history of haemorrhoids and notice any change in the pattern of bleeding, please have it reassessed.
For most painless rectal bleeding, seeing your GP within a few days is reasonable, and a specialist appointment usually follows within 1–2 weeks. Heavy bleeding, lightheadedness, dizziness, severe abdominal pain, or bleeding while on blood thinners is a reason to go to an emergency department on the day.
Make a few simple notes — when you first noticed the bleeding, the colour (bright red, dark, or mixed through the stool), whether there is also pain, and whether your bowel habit has changed. Bring a list of any medications, particularly blood thinners. A clear short history makes the consultation more useful for both of you.
Not always — your specialist will tailor investigations to your age, symptoms, and examination. For most adults with rectal bleeding, however, a colonoscopy is the most thorough way to identify the source and rule out anything serious, and it can often treat the cause (such as removing a polyp) in the same visit.
Need a specialist opinion?
If something in this article matches what you're experiencing, the most useful next step is a proper assessment. A GP referral is required.